[llvm] [Support]Look up in top-level subcommand as a fallback when looking options for a custom subcommand. (PR #71776)

[Fangrui Song via llvm-commits]

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@@ -525,6 +525,58 @@ TEST(CommandLineTest, LookupFailsInWrongSubCommand) {
   EXPECT_FALSE(Errs.empty());
 }
 
+TEST(CommandLineTest, SubcommandOptions) {
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MaskRay wrote:

There are other Subcommand tests. The name `SubcommandOptions` can be changed to reflect that the test intends to check, e.g. `TopLevelOptInSubcommand`

https://github.com/llvm/llvm-project/pull/71776